This application claims the priority of Swiss patent application 1448/99, filed Aug. 6, 1999, the disclosure of which is incorporated herein by reference in its entirety.
The invention relates a method for mathematically processing two quantities in an electronic circuit.
Analog addition circuits are usually based on the principle of current addition. Such adders are not always suitable for implementation in integrated circuits.
Hence, it is a general object of the invention to provide a method of this type that is suited for integration.
Now, in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the method for mathematically processing at least two values rx and ry in a combination circuit uses a combination circuit comprising two current inputs Ex,0 and Ex,1 for the value rx, two voltage inputs Ey,0 and Ey,1 for the value ry, two current outputs A0 and A1 for a result rz, and four transistors T0,0, T0,1, T1,0, T1,1, wherein the sources or emitters of the transistors T0,0 and T0,1 are connected to the current input Ex,0, the sources or emitters of the transistors T1,0 and T1,1 to the current input Ex,1, the gates or bases of the transistors T0,0 and T1,0 to the voltage input Ey,0, the gates or bases of the transistors T0,1 and T1,1 to the voltage input Ey,1, the drain or collector of the transistor T0,0 to the current output A0, the drain or collector of the transistor T1,1 with the current output A1, and the drains or collectors of the transistors T0,1 and T1,0 to a reference potential providing a saturation or forward polarization. The method comprises the steps of
feeding two input currents Ixpx(0) and Ixpx(1) through the current inputs Ex,0 and Ex,1, wherein a quotient of said input currents is equal to erx,
applying an input voltage between said voltage inputs Ey,0 and Ey,1 proportional to ry, and
generating, with said combination circuit, two output currents at the current outputs A0 and A1, wherein a quotient of said output currents is equal to erx+ry, and
deriving, from said output currents, a sum of the values rx and ry.
The method relies on a circuit consisting of transistors only. Every quantity is represented by a pair of currents or by a voltage between two voltage input terminals. If some quantity r is represented by a pair of currents, the ratio of the two currents corresponds to er; if it is represented by a voltage, the voltage corresponds to r. Transformations between these two representations can also be realized by simple circuits that consist of transistors only and can be integrated easily.
In references H. -A. Loeliger, F. Lustenberger, M. Helfenstein, F. Tarkxc3x6y, xe2x80x9cProbability Propagation and Decoding in Analog VLSIxe2x80x9d, Proc. of 1998 IEEE Intl. Symposium on Information Theory, Cambridge, Mass., 16-21 August 1998, p. 146 referred to as [1]), in F. Lustenberger, M. Helfenstein, H. -A. Loeliger, F. Tarkxc3x6y, and G. S. Moschytz, xe2x80x9cAn Analog Decoding Technique for Digital Codesxe2x80x9d, Proceedings of ISCAS ""99, Orlando, Fla., May 30-Jun. 2, 1999, vol. II, pp. 428-431 (referred to as [2]), as well as in H. -A. Loeliger, F. Tarkxc3x6y, F. Lustenberger, M. Helfenstein, xe2x80x9cDecoding in Analog VLSIxe2x80x9d, IEEE Communications Magazine, vol. 37, no. 4, April 1999, pp. 99-101 (referred to as [3]), a type of transistor network was presented by which a variety of signal processing algorithmsxe2x80x94in particular the decoding of error correcting codesxe2x80x94can be realized. These analog networks work with quantities that represent probabilities. The invention presented here expands the application of such networks to tasks that, at first sight, have nothing to do with probabilities. In particular, one circuit of [1] is now used as an adder. With such adders, a number of signal processing algorithms such as, for example, discrete-time adaptive analog filters can be realized as circuits with advantageous properties. In particular, networks containing both such adders and Gilbert-multipliers are suitable for preprocessing data that is subsequently processed by the probability networks presented in [1].
The claimed method can be.applied in a variety of ways, e.g. in correlators and filters.